Visualization of the Phase Decomposition Process Based on the Non-liner Diffusion Equation.

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A numerical analysis of the diffusion controlled phase transformation based on the non-liner diffusion equation is one of the main subjects in the field of the computer materials science. In the present study, we propose a new analyzing method of the nonlinear diffusion equation ("discrete type diffusion equation"), where the composition dependencies of atomic interaction energy, elasticity and mobility of atoms are taken into account so as to be able to calculate the phase decomposition in the real alloy system. Furthermore, the information of the solute atom occupation probability in atom site is also included in the proposed calculation theory. The proposed new method has a capability of predicting not only the phase decomposition in the disordered phases but also the other phase transformations such as the stress-induced precipitates coarsening, order/disorder phase transitions, phase decompositions in ordering alloys, the formation process of tweed structures, and so on. The purpo … More se of the present work is to reveal the nature of the phase transformation by visualizing the phase decomposition process. The detail behavior in diffusion controlled phase decomposition is calculated on the basis of the "discrete type non-linear diffusion equation". The results obtained are as follows.The two dimensional computer simulations were performed for the phase decomposition in the Fe-Mo, Fe-Cr, Al-Zn, and Cu-Co binary alloy systems on the basis of the new method. The thermodynamic data of phase diagram for these alloy systems was used in the present simulation. The microstructures theoretically calculated were well coincident with experimental facts of these alloy systems. Particularly, the typical features in the strain-induced microstructure changes were successfully calculated. Furthermore, we prepared the "Introduction Video" for the phase transformation by visualizing the calculated results based on the computer simulations. The detail behavior of the phase decompositions was presented by using the VTR,and this result will be very useful for the education in the field of materials science and engineering. Less